Brake



H. C. BOWEN June 15, 1937.

BRAKE Filed Feb. 27, 1936 INVENTOR Z #5655er C en/W i waya/ 422ATTORNEYS.

Patented June 15, 1937 UNITED vSTATES BRAKE Herbert C. Bowen, Detroit,Mich., assignor to Hydraulic Brake Company, Detroit, Mich., acorporation of California Application February 27, 1936, serial No.65,946

1s claims. (c1. 18s-79.5)

This invention relates to brakes, and more4 particularly to` brakes formotor vehicles.

Broadly the invention comprehends a brake A structure including a xedsupport, a rotatable 5 drum associated therewith, friction elements orshoes mounted on the support for cooperation with the drum, means formoving the shoes into engagement with the drum, and means forautomatically adjusting the friction elements or shoes to compensate forwear. Heretofore various means have been used fo automatically adjustingthe friction .elements o-r shoes of a brake to maintain a properrelation between the shoes and the drum. Generally such devices have notproved entirely satisfactory because vof an inherent overadjustment ofthe shoes due todrum distortion. It is the aim of the present inventionto overcome this ,difculty It has been well established that in brakestructures the relative position of the secondary or reverse shoe to thedrum remains substantially constant, and it is proposed to make use ofthis factor in the accomplishment of a satisfactory automatic adjustmentof the shoes.

An object of the invention is to provide a brake structure wherein anautomatic adjustment means for the primary or forward brake shoe iscontrolled by movement of the secondary or reverse brake shoe.

Another object of the invention is to provide' an automatic adjustmentfor the primary or forward brake shoe operated automatically by movementof the secondary or reverse brake shoe'onA both forward and reversebraking.

A further object of the invention is to provide a brake structureincluding a rotatable drum, a primary or forward brake shoe and asecondary or reverse brake shoe arranged for cooperation with the drum,means for moving the shoes into engagement with the drum, and means forautomatically adjusting the shoes with relation to the drum tocompensate for wear on the friction lining of the shoes including meansvariable in proportion to the expansion and contraction of the drumcaused by changes in temperature.

Fig. 1 is a vertical sectional view of a brake l structure taken justback of the head of the drum;

Fig, 2 is a cross-sectional View, substantially on line 2 2, Fig. l; and

Fig. 3 is a detail view, substantially on line 3-3, Fig. 2.

'Rcferrirg to the drawing for more specific details of-the invention, IUrepresents a xed sup- 55 port or backing plate having associatedthereerally at 28, including a cylinder 30 having there- With arotatable drum I2. Arranged on thebacking plate within the drum arecorresponding friction elements or shoes I4 and I6. The fric. tionelement or shoe I4 is a primary or forward brake shoe, and the frictionelement or shoe I6 5 is a secondary or reverse brake shoe. Each of l theshoes includes a web I8 supporting a rim 2U having suitably securedthereto frictional lining 22 -adapted for cooperation with the drum I2.

The articulate ends of the shoes are pivoted on the backing plate I0 asb-y pivotal supports 24 and 26, and suitably secured on the backingplate between the separable ends of the shoes is a iluid pressureactuated motor indicated gen- 15 in opposed pistons 32 and 34. Thevpistons have on their respective heads leak-proof cups 36 and 38, and acoil spring 40 interposed between the cups serves to retain them againstdisplacement and to provide a suitable spacer for the pistons when intheir retracted positions. The pistons have in-their backs recesses 42and 44 for the reception of the separable .ends of the shoes, and aretractile spring 46 connecting the shoes serves to retain the shoes inclose engagement with the pistons and to return the shoes to their on orretracted positions at the end of each braking operation.

Mounted for rotation in the backing` plate adjacent the forward brakeshoe is a'stub shaft 48. One end of this shaft extends into the drum I2and is provided with a head 50, and its other end extends voutwardlyfrom the backing plate. A sleeve 52 tted on the shaft between the head5I] and the backing plate I0 has a cross arm 54, one end of whichterminates in a spherical member 56 adapted to engage a stop 58 on theforward brake shoe I4 substantially' centrally of the overall length ofthe shoe, and the other end of the arm 54 has an aperture 60, thepurpose of which will "hereinafter appear.

Sleeved on that end of the shaft 48 extending outwardly from the backingplate is a spring 62, preferably of the four-tine type, and threaded onthe shaft is a nut 64 secured against displacement by a conventionallocknut 66. By tightening the nut A64 the spring 62 may be placed undercompression to clamp the sleeve 52 between the head 50 on the shaft 48and the 'backing plate I0. This results in setting up frictionalresistance to rotation of vthe sleeve and hence movement of the crossarm 54 formed integral with the sleeve.

A sectionalized rod indicated generally at 68 connects the cross arm 54to the secondary or reverse brake shoe I8. As shown, the rod includes a.section 18 having a reduced 'end' portion 12 extending throughtheaperture 88 in the cross arm 54. This reduceddend portion is threadedfor the reception of a nut 14, and a spring 18 is sleeved on the reducedend portion between the cross arm and the nut. The spring 18 is ofgreater tensional strength than theresistance. to rotation of the sleeve52 introduced e by the spring 82.

A metallic rod 18 having a relatively large coefficient of thermalexpansion is suitably convnected at one of its ends to the section 18,and

threaded sleeve 82.

the other end of the rod 18 is suitably connected to a short rod section88 having an internally This sleeve is aligned with a correspondinginternally threaded sleeve 84 having an off-set clevis 88 secured to thereverse shoe I8 by a pivot pin 88 in the web of the secondary or reverseshoe adjacent its free end. The pin 88 has a small clearance 88 in theweb of the shoe providing for slight unhampered movement of the shoe.'I'he aligned sleeves 82 and 84 receive a right and left-hand threaded'member 98 provided with a star wheel 82 held against rotationby a springclip 84 secured to the sleeve 88. By rotating the wheel 92 the length ofthe rod 88 may be increased or decreased to adjust the shoes withrelation to the drum.

When the brake is in the on position or in the position of rest, theshoe I4 Ais retained against the spherical end 58 of the cross arm 54,and the shoe -I8 is heldy against the pin 88` in the clevis 88 by theretractile spring 48. Under` these conditions, upon an application ofthe brake while thevehicle is moving forwardfthe shoes I4 and I8 aremoved by the iluid pressure actuated motor 28 into engagement with thedrum, resultingin retardation of the drum.

Should Vthe brake be applied. for a suiilcient length of time tocausetheydrum to expand, because of heat generated between the frictionelements or shoes and the drum, the bar or rod 88,-

having a relatively large coeiiicient of thermal expansion, also expandsdue to heat absorbed from the brake. Hence, when-the brake-is releasedand the shoes' returned to the oif or retracted postion, under theinfluence of the re-4 tractile spring 48, they are retained in properspaced relation to the vdruxn for subsequent oper` ations, and, sincethe bar llhcools and contracts proportionately to the cooling andcontracting of the drum, the spaced vrelation of the shoes withV Vgagement with the drum during ya normal brake application. As this shoesmoves into engagement with the drum, the clearance inthe web of the shoearound the pivot pin `88 is taken up and a pullis exerted on the rod 88,and this force is transmitted through the spring 18 to the. cross arm 84to rock the arm on the shaft 48, resulting f shoe I4.

position, and the other end of the arm 54 is connected to one end of therod 88, the other end of which carries the pin 88providing a stop forsupporting the shoe I8 when this shoe is in retracted position.

It is inherent in brake structures for the lining ofthe primary orforward brake shoe to wear faster than the lining of the secondary orreverse brake shoe. This diil'erential inthe wear ofthe linings of therespective brake shoes is provided for by theV automatic adjustmentmechanism which is so connected between the primary and secondary shoesthat movement of the secondary shoe is multiplied when transferred. tothe primary shoe. It is to be observed that the automatic adjustmentmechanism is connected to the secondary shoe adjacent to the free end ofthe' 'shoe and engages Athe primary shoe substantially -ferred to theprimary shoe.

During a brake application, while the vehicle .is moving backward, thebrake shoes I4 and I8 vare moved into engagement -with the drum I2 bythe fluid pressure actuated motor 28 as in forward braking. However,under this condition the shoe I8 becomes the forward braking shoe andthe shoe I4 becomes the reverse braking shoe, and since the brake shoeI8 `when operated under these conditions performs the greater proportionof the work, its movement, due to drum,

distortion, is greater than when functioning as a reverse brake shoe.

This increased movement results in exerting a pull on the rod 88, andthis force is transmitted through the 'springs 18 to the arm 54. 'Ihisarm is held against any appreciable movement by the Due to drumdistortion, movement of this shoe is practically nil, and hence anymaterial movement' of the arm 54 is inhibited. Slight movement of theshoe I4 may occur upon initial application of the brake; however, as thedrum becomes distorted the shoe returns to engage the Under theseconditions, when the brake is released and the shoes returned to theiroff or retracted positions by the retractile spring 48, the spring 18functions to return the rod 18 to the position it maintained prior tothe reverse braking operation, with the result that the shoes are againadjusted in proper spaced relation to the drum.

Although this invention has been described in connection lwith certainspecific embodiments, the principles involved' are susceptible ofnumerous other applications that will readily occur to persons skilledin' the art. The invention is,

therefore, to be limited only as indicated by the scope of the appendedclaims.

Having thus described the various features of the invention,what I claimas new and desire to secure by Letters Patent is:--

1. A vehicle brake comprising a primary brak- -ing element and asecondary braking element,

and an adjustable stop for the primarybraking element connected to andactuated by the secondary braking element during forward movement of thevehicle.

2. A vehicle brake comprising a primary braking element,l a secondarybraking element, a stop l is travelling in a forward direction, saidmeans including means for compounding the movement of the secondarybraking element when transferring such movement to the stop.

4. A vehicle brake comprising a primary braking'element and a secondaryAbraking element, an actuator for the braking elements, a retractor stopfor the primary braking element, means operable while the vehicle istravelling in a forward direction for automatically adjusting the stopby movement of the secondary braking element and for compounding themovement of the secondary braking element when such movement istransferred to the stop.

5. A vehicle brake comprising a primary braking element and a secondarybraking element, an actuator for the braking elements, a movableretractor stop for the primary braking e1ement,,

means for transferring movement of the sec--l ondary braking element tothe stop while the vehicle is travelling in a forward direction, and

means for compounding the movement when between the rod and, theadjustable stop, and a lost motion connection between the rod and theecondary braking element.

-'7. A brake comprising a primary braking element, a secondary brakingelement, an actuator for the braking elements, an adjustable stop forthe primary braking element adapted to sup-' port the primary brakingelement substantially centrally of its length, and means connecting thefree end of the secondary braking element to the stop operative tocompound the movement of the secondary braking element when suchmovement is transferred to the stop.

8. A brake comprising a primary braking element,i a secondary brakinge1ement, an actuator for the braking elements, an adjustable stop forsupporting the primary braking element substantially centrally of itslength, an adjustable rod, a lost motion connection between one end ofthe rod and the step, and a lost motion connection between the other endof the rod and the free end of the secondary braking element.

9. A brake comprising a xed support, a drum associated therewith,braking elements on the lsupport for cooperation with the drum, anactuator for the braking elements, a stop for one of the brakingelements, said stop being adjustable relative toI said braking element,and a rod connecting the adjustable stop tothe other braking 'element.

including a rockable member, means resisting movement of the rockablemember, and means connecting the rockable member to the other brakingelement.

11. A brake comprising a xed support, a rotatable drum associatedtherewith, a primary braking element and a secondary braking elementmounted on the support for vcooperationl with the drum, adjustable stopsfor the braking elements including a rockable member adjacent theprimary braking element, and a member connecting the rockable member tothe secondary braking element.

12. A brake comprising a fixed support, a rotatable drum associatedtherewith, a primary braking element and a secondary braking elementarranged on the supportffor cooperation means frictionally resistingmovement of the arm, and a rod connecting the arm to the sec-A ondarybraking element.

13. A brake comprising a xed support, a ro-` tatable drum associatedtherewith, a primary braking .element and a secondary braking elementarranged on the support forn'cooperation with the drum, an actuator forthe braking elements, an arm pivoted on the support and adapted toengage the primary braking element, an adjustable rod, a lost motionconnection between the rod and the arm, and a lost motion connectionbetween the rod and the secondary braking element.

14. A brake comprising a xed support, a ro-v tatable drum associatedtherewith, a primaryl braking element and a secondary braking elementarranged on the support for cooperation with the drum, an actuator forthe braking elements, an arm pivoted on the .support and adapted toengage the primary braking element,

means resisting movement of the arm, an'ad justable rod, a lost motionconnection 'between one end of the rod and the arm, and a pin in theother end of the rod received by a slot in the web of the secondarybraking element.

15. A brake comprising a fixed support, a rotatable .drum associatedtherewith, a primary braking element and a secondary braking elementarranged onvthe support forcooperation with the drum, an actuatorfor'the braking elements, a cross arm pivotally mountedon the support,means frictionally resisting movement of the arm, one end of the armproviding astop for the primary braking element, and la rod hav-4 inghigh thermostatic characteristics connecting A the other end ofthe'cross -arm to the secondary braking element.

16. A brake comprising a xed support, a rotatable drum associatedtherewith, a primary braking element and a secondary braking elementmounted on the support vfor cooperation with thedrum, an actuator forthe braking elements, an adjustable stop for the primary braking elementmounted on the support substantially centrally of the element, a rod ofhigh thermostatic characteristics, means for adjustingthe overall lengthofthe rod, a lost motion connection between one end of the rod vand theadjust able stop, and a lost motion connection between the other end oftherod and the free end of the secondary braking element.V

HERBERT C. BOWEN.

